1. Field of the Invention
The present invention relates to an electromagnetic analysis apparatus for obtaining electromagnetic spectrum information In particular, the present invention relates to an analysis apparatus for obtaining spectral information of an electromagnetic wave in the frequency range from millimeter-wave band to terahertz band (30 GHz to 30 THz).
2. Description of the Related Art
Techniques are being developed for nondestructive sensing with an electromagnetic wave in the frequency range from a millimeter-wave band to a terahertz band (30 GHz to 30 THz, hereinafter referred to simply as a terahertz (THz) wave). The electromagnetic wave in this frequency range is applied, for example, to safe imaging in place of X-ray fluoroscopic inspection; spectrometric investigation of physical properties by measuring absorption spectrum or complex dielectric constant in the interior of substances; analysis of a biological molecules; evaluation of concentration and mobility of carriers; and so forth.
On the other hand, an analysis apparatus is disclosed which measures optical spectrum by use of an spectroscopic prism and a CCD line image sensor having no mechanical angle-changing mechanism (Japanese Patent Application Laid-Open No. H06-026930 (hereinafter referred to as “Patent Document 1”)). With this apparatus, the light to be measured is converted to a parallel light beam by an optical lens system; the light beam is introduced to a spectroscopic prism of fixed deflection; the entire of the spectrum of the light is converted simultaneously into electric signals by a CCD image sensing element, and is corrected by a correction circuit for the wavelength-sensitivity characteristics of the CCD image sensing element; and from the corrected signals, the characteristic spectrum distribution of the light is derived.
Further, a small-sized near-infrared spectral apparatus is disclosed which detects a near-infrared spectrum with a high resolving power, high dynamic range, and high sensitivity (Japanese Patent Application Laid-Open No. 2005-121574 (hereinafter referred to as “Patent Document 2”)). The near-infrared spectral apparatus has an input terminal, a diffraction grating, and plural output terminals. The input terminal is placed on the Rowland circle, and the near-infrared light is introduced to the input terminal. The diffraction grating is placed on the Rowland circle and forms spectrum of monochromatic light components. The output terminals are placed on the Rowland circle at the positions where the spectra are focused at nonuniform intervals to decrease the positional deviation of the output terminals from the spectrum-focusing spot.
The present invention is directed to an analysis apparatus for analyzing a specimen, comprising a spectral separator for dispersing spatially an electromagnetic wave introduced from the specimen into spectral components, a sensing element array containing plural sensing elements for sensing the spectral components of the electromagnetic wave dispersed spatially by the spectral separator, and a spectrum calculator for calculating the spectrum from the signal sensed by the sensing elements; the sensing element array having sensitivities different to each of the spectral components of the electromagnetic wave dispersed spatially by the spectral separator, and the spectral separator and the sensing element array being placed so as to receive the spectral components by each of the sensing elements at different incident angles.
The sensing element array can have a constitution for maximizing the sensitivity of sensing of the electromagnetic wave for each of the spectral components dispersed spatially by the spectral separator, the spectral separator and the sensing element array being placed so as to introduce the spectral components to each of the sensing elements at incident angles to maximize the sensitivity of each of the sensing elements.
The electromagnetic wave can cover at least a part of a frequency range from 30 GHz to 30 THz.
The sensing element can have an electromagnetic wave sensor and a filter for selecting the wavelength range for sensing the electromagnetic wave introduced from the specimen; the filter can be constituted of a negative dielectric medium having a negative real part and a second medium; and the negative dielectric medium and the second medium are placed at a distance of not more than the wavelength of the electromagnetic wave to be sensed, and the filter and the electromagnetic wave sensor can be placed at a distance of not more than the wavelength of the electromagnetic wave to be sensed.
The sensing element array can have a plurality of the sensing elements placed on a Rowland circle in accordance with the wavelength dispersion characteristics of the spectral separator.
The apparatus can have a means for compensating deviation of the incident angle or incident position of the electromagnetic wave onto the sensing element.
The sensing element array can receive the electromagnetic wave from a linear region of the specimen; and the spectrum calculator can calculate spectra at plural positions in the linear region.
The apparatus can have a fiber array; the fiber array can receive the electromagnetic wave dispersed spatially into spectral components by the spectral separator and transmits the received electromagnetic wave to the sensing element array; and the electromagnetic wave leaving the fiber array can be introduced to the sensing element to obtain the maximum sensitivity to the sensing element which is designed to give the maximum sensitivity to each of the wavelengths.
In the analysis apparatus, at least one of the spectral separator and the sensing element array can be integrated into a unit, and the unit can be exchangeable.
The apparatus can have a means for projecting the electromagnetic wave onto the specimen.
The present invention is directed to an analysis apparatus for analyzing a specimen, comprising a generator for generating an electromagnetic wave; a diffraction grating for dispersing spatially an electromagnetic wave generated by the generator into spectral components; a sensing element array having a plurality of plasmon type sensing elements for sensing the spectral components of the electromagnetic wave dispersed spatially by the diffraction grating; and a spectrum calculator for calculating the spectra from the intensity of the electromagnetic wave detected by the sensing elements; the sensing element array being constituted to maximize a sensitivity for detecting each of the spectral components of the electromagnetic wave separated spatially by the diffraction grating; and the diffraction grating and the sensing element array being placed so as to introduce the spatially dispersed spectral components to each of the sensing elements at an incident angle to maximize the sensitivity of each of the sensing elements.
However, the method employing the apparatus of the above Patent Documents 1 or 2 tends to give lower sensitivity since no consideration is made on the wavelength dependency of the incident angle for the maximum sensitivity of the sensing element. Therefore, the high-sensitivity and high-speed analysis cannot readily be conducted.